Embedded video is black but with audio, but the video works fine on youtube.

I'm having trouble with firefox not been able to display embedded video on sites.
I see the preview image but when i start play all video area becomes black and I can hear the audio playing. I also can pause the "video".

If I start firefox in safe mode, it works.
I have deactivated all my extensions/add-ons, without any success.
I have reset all cache, no success
I have restored to factory result, no success
I have uninstalled firefox, and deleting all local data and reinstalled firefox, still same problems.

I have tested to go to http://www.youtube.com/html5 and activated the html5 player, and then I see the play button, progressbar and volume etc, but still no video.

The video is working fine in IE 9 and Chrome (unknown version, but since it autoupdates it's probably the latest)

I'm having trouble with firefox not been able to display embedded video on sites.
I see the preview image but when i start play all video area becomes black and I can hear the audio playing. I also can pause the "video".
If I start firefox in safe mode, it works.
I have deactivated all my extensions/add-ons, without any success.
I have reset all cache, no success
I have restored to factory result, no success
I have uninstalled firefox, and deleting all local data and reinstalled firefox, still same problems.
I have tested to go to http://www.youtube.com/html5 and activated the html5 player, and then I see the play button, progressbar and volume etc, but still no video.
The video is working fine in IE 9 and Chrome (unknown version, but since it autoupdates it's probably the latest)

Nyttigt svar

As I wrote, I now have zero extensions but I do have plugins. But as I see they are not disabled when I run in safe mode and in safe mode it works.
Also, the video works if I go directly to youtube, but not if I view it embedded/in a iframe.

As I wrote, I now have zero extensions but I do have plugins. But as I see they are not disabled when I run in safe mode and in safe mode it works.
Also, the video works if I go directly to youtube, but not if I view it embedded/in a iframe.

So I unchecked the box: "Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" and the embedded video starting playing VIDEO! Thanks for that. Now I'm curious if it should work however with it clicked though?

So I unchecked the box: "Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" and the embedded video starting playing VIDEO! Thanks for that. Now I'm curious if it should work however with it clicked though?